Stock and Other Incentive Plans - Amortization of Compensation for Nonvested Shares (Details) $ in Millions	Dec. 31, 2017 USD ($)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
2018	$ 9.4
2019	7.0
2020	6.7
2021	5.7
2022	3.2
2023 and thereafter	3.6
Total	$ 35.6